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How does facebook, gmail send the real time notification?

I have read some posts about this topic and the answers are comet, reverse ajax, http streaming, server push, etc. 5 Answer...
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C dynamically growing array

I have a program that reads a "raw" list of in-game entities, and I intend to make an array holding an index number (int) of an indeterminate number of entities, for processing various things. I would like to avoid using too much memory or CPU for keeping such indexes... ...
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UITableView : viewForHeaderInSection: not called during reloadData:

I've set up the tableview with correct delegate and datasource linkages.. the reloadData method calls the datasource and the delegate methods except for viewForHeaderInSection: . ...
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Why we should not use protected static in java

...able exists at class level, it does not exist separately for each instance and it does not have an independent existence in classes which extend me. Think about what protected means: This variable can be seen by this class, classes in the same package and classes which extend me. The two mea...
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Generate random numbers following a normal distribution in C/C++

How can I easily generate random numbers following a normal distribution in C or C++? 18 Answers ...
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Good PHP ORM Library?

...ates everything on the fly) No models etc. It even does all the locking and transactions for you and monitors performance in the background. (Heck! it even does garbage collection....) Best of all... you don't have to write a single... line of code... Jesus this, ORM layer, saved me ass! ...
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Convert PEM to PPK file format

...EM files to PPK files? (you may guess that Amazon EC2 gives me a PEM file, and I need to use the PPK format for SSH connectivity). ...
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What are the differences between double-dot “..” and triple-dot “…” in Git commit ranges?

Some Git commands take commit ranges and one valid syntax is to separate two commit names with two dots .. , and another syntax uses three dots ... . ...
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What exactly do “u” and “r” string flags do, and what are raw string literals?

...no "escape sequences" to represent newlines, tabs, backspaces, form-feeds, and so on. In normal string literals, each backslash must be doubled up to avoid being taken as the start of an escape sequence. This syntax variant exists mostly because the syntax of regular expression patterns is heavy w...
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Java generics - why is “extends T” allowed but not “implements T”?

...lass 'implements' or 'extends'. The constraint possibilities are 'extends' and 'super' - that is, is this class to operate with assignable to that other one (extends), or is this class assignable from that one (super). share...